This invention relates to matrix composites and processes for making them.
A fiber-reinforced composite, or matrix composite, is an article comprising a plurality of fibers (the reinforcement) embedded in a plastic (the matrix). Typically, the fibers give strength and/or stiffness to the composite, and the matrix maintains fiber alignment and transfers load around broken fibers. Matrix composites are described in detail in numerous references, such as Kirk-Othmer Ency. Chem., Tech. - Supp., Composites, High Performance, at 260-281 (J. Wiley & Sons 1984).
A number of fibers are available for use in matrix composites, each having different combinations of tensile and compressive strength and modulus, temperature stability, creep, cost, and other properties. Suitable fibers may contain, for example, aramid (such as Kevlar.TM. fibers), boron, glass, carbon, gel-spun polyethylenes (such as Spectra.TM. fiber), polybenzoxazole, polybenzothiazole, or polybenzimidazole. Suitable fibers and processes for their fabrication are described in numerous references, such as U.S. Pat. No. 4,533,693; 3 Kirk-Othmer Ency. Chem. Tech., Aramid Fibers, 213 (J. Wiley & Sons 1978); Kirk-Othmer Ency. Chem , Tech. - Supp., Composites, High Performance, at 261-263: 11 Ency. Poly. Sci. & Eng., Polybenzothiazoles and Polybenzoxazoles, 601 (J. Wiley & Sons 1988) and W. W. Adams et al., The Materials Science and Engineering of Rigid-Rod Polymers, at 245-312 (Materials Research Society 1989).
A number of matrix materials are also available for use in matrix composites. Some matrix materials are thermosetting resins, such as polyesters, epoxy resins, polycyanates, polybutadienes, vinyl ester resins, polyimides, and even carbon. Some matrix materials are thermoplastic, so that the resulting matrix composite may be shaped at a temperature above the processing temperature of the matrix.
There is a need for improved thermoplastic matrix materials in matrix composites. In particular, a matrix having a higher tensile strength and modulus would improve those same physical properties in the matrix composite as a whole. What is needed is a prepreg in which the fiber is impregnated with an improved thermoplastic matrix resin.